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The Axles of SUV And Pickup Truck of the Year #FWOTY19

Posted in Events on December 7, 2018
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Photographers: Harry Wagner

We love axles; they help get rotational engine forces from the engine, transmission, and transfer case to the tires and wheels. Most folks in four-wheeling land understand most of the axle terminology we focus on—solid versus independent, axle ratios, limited-slip differentials, lockers, and vehicle traction controls, or at least the general idea of them. What these terms all really boil down to are how strong the parts are, what tires turn and when, and how they go over the bumps and humps in the trail. We spend an inordinate amount of time worrying about what axles are where, the general sizes of parts, and what does what. Forgive us—we are nerds, 4x4 nerds. Luckily, you too can benefit from our nerdiness as we geek out on what axles spin the tires of the SUVs and pickups from our annual 2019 of the Year testing.

SUV of the Year

Jeep Wrangler JL

The Jeep JL Rubicon has a pair of third-generation “Dana 44 HD” axles with electronic lockers and 4.10:1 axle ratios. We added quotations on the Dana 44 part since we have it on good authority that these Dana 44s do have plenty of Dana DNA, but are “Dana 44s” in name only. They feature Dana’s AdvanTEK technology, with additional strength designed into what is basically an all-new axle despite the nomenclature.

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Jeep Cherokee Trailhawk

The Jeep Cherokee Trailhawk has Active Drive Lock 4WD, with an electronic locking rear axle. Axle ratios are 3.73:1 with the turbo 2.0L I-4, and Jeep claims a 20:1 crawl ratio. However they are getting it, the Cherokee does have low enough gearing to crawl, blast around in sand, and also in light mud. The axles are independent and use aluminum-housed differentials front and rear.

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Land Rover Range Rover PHEV

The axles are independent and use aluminum-housed differentials front and rear. Our Range Rover HSE PHEV (the fancy one) has Terrain Response 2 selectable driving and off-road modes and Electronic Active Differential with Torque Vectoring by Braking. This Rover (as well as the other Rover in our test) has a center and rear axle locking differential.

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Land Rover Range Rover Sport PHEV

The axles are independent and use aluminum-housed differentials front and rear. This sportier version of our two Range Rovers also has a Twin Speed Transfer Box, Terrain Response 2 selectable driving and off-road modes, and Electronic Active Differential with Torque Vectoring by Braking (that’s their language, we’d probably just call it electric traction control with locking center and rear diffs). We are still nagging our sources for more details on these differentials, like ring gear size and more. We’ll be sure to update you when we find out.

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Toyota 4Runner TRD Pro

It has a part-time 4WD system with Active TRAC, Multi-Terrain Select, and Toyota’s venerable rear Electronic Locking Differential. Axle ratios are 3.73:1. The front differential on this 4Runner is Toyota’s classic 8-inch ring gear in a steel clamshell housing. Rear axle is a Toyota 8.2 (sometimes called an 8.4) semi-float axle. Whatever is there, Toyota’s traction control system is dialed and they work.

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Pickup Truck of the Year

Chevy Silverado 1500 Trail Boss

So for 2019 GM muddied the axle identification waters by introducing a new in-house, GM-built rear axle or a familiar rear axle from AAM in their 1/2-ton trucks. Problem is, the new GM axle is so new no one is exactly sure how to tell them apart. Both of our trucks have 3.23:1 axle gears with GM-supplied front differentials, but we’re making some educated guesses on the rear axles for now. We are about 99 percent confident that our Chevy Silverado 1500 Trail Boss has the new GM in-house rear axle with the Gov-lok (G80) for added traction. Front axle is a GM independent front suspension axle with an open differential and a GM-sourced 8.25-inch ring gear in aluminum housing.

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GMC Sierra 1500 AT4

The GMC claims a Heavy-Duty locking rear differential on the paperwork GMC gave us and also has a GM-based, aluminum-housed front IFS 8.25-inch diff with 3.23:1 gearing. This rear axle (we are betting) is the AAM 250mm (9.75-inch) axle with a good old-fashioned Gov-lok automatic locking differential. GM loves Gov-loks (sometimes called G80s). Since they are wheel-speed sensitive we guess they are better than an open diff, but we’d really prefer a selectable locker, or an automatic locker that is more consistent like a Detroit Locker

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Ram 1500 Rebel

That rear axle sure looks like the classic Chrysler corporate 9.25 rear axle (which they sometimes call a 235mm Chrysler), and according to Ram the axle has been “re-worked” for 2019. We suspect that has only to do with the switch from 5-lug to 6-lug to increase load carrying capacity, but don’t know for sure. One way or another, this axle is stuffed with a 3.92:1 axle ratio and an electronic locking rear differential. We love that! We are betting the front axle in the new Ram Rebel, which has independent suspension, is similar to the old ZF 215mm with an aluminum centersection and like gears.

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Toyota Tundra TRD Pro

The Toyota Tundra TRD Pro has a 10.5-inch ring gear with 4.30:1 gears and uses Toyota’s Automatic Limited-Slip Differential (Auto LSD), which uses brakes to achieve an electronic equivalent of your standard limited-slip differential. The 4x4 system also uses Toyota’s Active Traction Control A-TRAC system when in four-wheel drive. The Tundra’s front differential is in its independently suspended front 8.7-inch (some call it a 9--inch) diff with like gears.

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